1. Field of the Invention
The present invention relates to a solid-state imaging device, an imaging device, and a signal reading method. Particularly relates to a solid-state imaging device and an imaging device in which a first substrate and a second substrate which have circuit elements constituting pixels disposed therein are electrically connected to each other. In addition, the present invention relates to a signal reading method of reading a signal from a pixel.
2. Description of Related Art
In recent years, video cameras, electronic still cameras and the like have generally been in widespread use. CCD (Charge Coupled Device)-type or amplification-type solid-state imaging devices are used in these cameras. Amplification-type solid-state imaging devices guide signal charge, generated and accumulated by a photoelectric conversion section of a pixel on which light is incident, to an amplification section provided in the pixel, and output a signal amplified by the amplification section from the pixel. In the amplification-type solid-state imaging devices, a plurality of such pixels is arranged in a two-dimensional matrix. The amplification-type solid-state imaging devices include, for example, a CMOS-type solid-state imaging device using a CMOS (Complementary Metal Oxide Semiconductor) transistor, and the like.
In recent years, CMOS (Complementary Metal Oxide Semiconductor)-type solid-state imaging devices (hereinafter, referred to as “MOS-type solid-state imaging devices”) have attracted attention as a solid-state imaging device, and have been put to practical use.
Such a MOS-type solid-state imaging device can be driven with a single power supply unlike the CCD (Charge Coupled Device)-type solid-state imaging device. In addition, the CCD-type solid-state imaging device requires dedicated manufacturing processes, whereas the MOS-type solid-state imaging device can be manufactured using the same manufacturing processes as those of other LSIs. For this reason, the MOS-type solid-state imaging device easily deals with an SOC (System On Chip), and can realize the multi-functionalization of the solid-state imaging device.
In addition, the MOS-type solid-state imaging device includes an amplifier circuit in each pixel and thus amplifies signal charge within the pixel. For this reason, the MOS-type solid-state imaging device has a configuration which is hardly influenced by noise from a signal transmission path. Further, the MOS-type solid-state imaging device is characterized in that the signal charge of each pixel can be selected and extracted (selection scheme), and the accumulation time or the reading order of signals can be freely controlled for each pixel in principle.
Previously, in the general CMOS-type solid-state imaging devices, a scheme in which signal charge generated by a photoelectric conversion section of each of the pixels arrayed in a two-dimensional matrix is sequentially read for each row, has been adopted. In this scheme, the exposure timing in the photoelectric conversion section of each pixel is determined by the start and termination of the reading of signal charge, and thus the exposure timing is different for each row. For this reason, when an image of a fast-moving subject is captured using such a CMOS-type solid-state imaging device, the subject is distorted with a captured image.
Previously, as exposure types of general MOS-type solid-state imaging devices (hereinafter, referred to as a “solid-state imaging devices”), a line exposure type and a global exposure type have been known. In the line exposure type, a large number of pixels arrayed two-dimensionally within the solid-state imaging device are exposed at the timing different for each row. The line exposure type is a type in which a video signal of a subject is obtained by sequentially reading signal charge generated after performing exposure of a row of a certain unit by the photoelectric conversion element within pixels in the row. In the case of the line exposure type, exposure and reading can be continuously performed in row units. For this reason, it is possible to obtain a video signal of a subject in a state in which the influence of noise generated in an accumulation section that accumulates the signal charge generated by the photoelectric conversion element is suppressed to a minimum. However, when an image of a moving subject is captured in the line exposure type, an image of the subject cannot be correctly captured due to the exposure timing different for each row.
On the other hand, the global exposure type is a type in which all the pixels arrayed two-dimensionally within the solid-state imaging device are exposed at a synchronous timing. In the case of the global exposure type, since all the pixels are exposed at a synchronous timing, a distorted video is never obtained even at the time of capturing an image of the moving subject. However, in the global exposure type, since the signal charge generated by the photoelectric conversion element within the pixel is sequentially read after all of the pixels are exposed, it is difficult to suppress the influence of noise generated in the accumulation section in the pixels that require a long time until the reading of the signal charge is started after terminating exposure. For this reason, in the global exposure-type solid-state imaging device, a video signal having large noise is obtained more often than in the line exposure-type solid-state imaging device.
In the global exposure-type solid-state imaging device, a circuit for suppressing the influence of noise generated in the accumulation section as mentioned above is added to the solid-state imaging device, thereby allowing a video signal in which the influence of noise is suppressed to a minimum to be obtained even in the solid-state imaging device in which the global exposure type is adopted.
In order to eliminate the distortion of a subject, a simultaneous imaging function (global shutter function) of realizing the simultaneity of the accumulation of signal charge is proposed. In addition, the CMOS-type solid-state imaging device having a global shutter function is increasingly being used. In the CMOS-type solid-state imaging device having a global shutter function, generally, it is necessary to include an accumulation capacitance section having a light-shielding property in order to accumulate the signal charge generated by the photoelectric conversion section until reading is performed. In such a CMOS-type solid-state imaging device in the related art, after all the pixels are simultaneously exposed, the signal charge generated by each photoelectric conversion section is simultaneously transferred to each accumulation capacitance section in all the pixels and is temporarily accumulated. The signal charge is then converted sequentially into a pixel signal at a predetermined reading timing and is read.
Japanese Unexamined Patent Application, First Publication No. 2006-49361 discloses a solid-state imaging device in which a MOS image sensor chip having a micro-pad formed on a wiring layer side for each unit cell and a signal processing chip having a micro-pad formed on the wiring layer side of a position corresponding to the micro-pad of the MOS image sensor chip are connected to each other by a micro-bump. In addition, Japanese Unexamined Patent Application, First Publication No. 2010-219339 discloses a method of preventing an increase in a chip area using a solid-state imaging device in which a first substrate having a photoelectric conversion section formed therein and a second substrate having a plurality of MOS transistors formed therein is bonded to each other.
Japanese Unexamined Patent Application, First Publication No. 2006-49361 discloses a method of which creating a pixel circuit section of a MOS-type solid-state imaging device as a pixel circuit chip; creating a signal processing section as a signal processing chip; and superimposing the chips which are separately created. In the art disclosed in Japanese Unexamined Patent Application, First Publication No. 2006-49361, the pixel circuit chip and the signal processing chip which are separately created are connected to each other through a bump.
Japanese Unexamined Patent Application, First Publication No. 2006-49361 is configured such that a cell of the MOS image sensor chip includes a photoelectric conversion element, an amplifying transistor and the like (FIGS. 5 and 12 of Japanese Unexamined Patent Application, First Publication No. 2006-49361), and a cell of the signal processing chip digitizes a signal which is output from the cell of the MOS image sensor chip and then stores the signal in a memory (FIGS. 8 and 9 of Japanese Unexamined Patent Application, First Publication No. 2006-49361).
In Japanese Unexamined Patent Application, First Publication No. 2010-219339, circuit elements constituting pixels having a global shutter function in the related art are separately disposed in two substrates (FIG. 9 of Japanese Unexamined Patent Application, First Publication No. 2010-219339). In addition, a phenomenon, in which noise caused by light incident on the pixel during a waiting period until signal charge accumulated in an accumulation capacitance section of a MOS image sensor chip is read moves from a MOS image sensor chip to a signal processing chip, is suppressed.